1. Field of the Invention
This invention relates to semiconductor storage cabinets known as xe2x80x9cstockersxe2x80x9d and more particularly relates to a semi-open architecture xe2x80x9ckioskxe2x80x9d storage cabinet or stocker.
2. Background Information
Semiconductor wafer fabrication involves hundreds of processes for producing electronic chips or integrated circuits such as microprocessors, computer memory and other microcircuits. Throughout the fabrication process, the semiconductor wafers are transported from one processing station or area in sealed containers or cassettes. The semiconductor wafers must be kept in a class 1 substantially contaminant-free environment throughout the fabrication processing.
Between processing steps the sealed containers for the semiconductor wafers are stored in enclosures known as stockers. Each container may have up to seventy-five 300 mm (12 inch) semiconductor wafers. The containers are manually or by an automatic transfer and transport system moved out of the stockers through a port or window to a processing station. After each process is complete, the semiconductor wafers are returned to the container and then usually delivered back to the stocker to await further processing or to another stocker at the next processing step. There may be many stockers strategically placed at intervals along the production line for easy access by personnel performing the processing.
The stockers have a plurality of open frame slots or shelves inside a substantially rectangular enclosure. Semiconductor wafer containers are returned or retrieved through a port or window in the stocker. After a particular process is complete, the semiconductor wafer container is either manually or by an automatic transport system returned to a shelf at the in/out window or port. An automatic pick up and transfer apparatus picks up the semiconductor wafer container and places it in an empty slot or shelf in the stocker to await the next processing step.
The pick up and transfer apparatus is a three-axis robot comprised of a linear arm that moves vertically, rotationally, and horizontally inside the stocker. The robot has a paddle for picking up a container and is driven by several programmed servo motors. Vertical and rotational movement of the linear arm is performed by the programmed servo motors. Another servo motor moves the paddle horizontally in and out into position beneath a container. The system always knows where there is an empty slot or shelf in the stocker. Once a semiconductor wafer container is placed in the input port or window, the pick up and transfer apparatus is triggered automatically or by an operator to move into position vertically and rotationally and moves the paddle horizontally to pickup the container. The paddle with the container is then retracted and the pick up and transfer apparatus quickly moves inside the stocker to a position adjacent an empty slot or shelf. The robot then deposits the container on the shelf and is retracted and the linear arm returned to a standby position to await the next semiconductor wafer container being retrieved or stored. The retrieval of a semiconductor wafer container from the stocker is just a reversal of the process of storing a container described above.
A disadvantage of this type of stocker is the time to retrieve and store semiconductor wafer containers. Since there is usually only one input port or window, the system or operator must wait until pickup and transfer apparatus retrieves and stores a container placed at the input port and then return to retrieve another container. This makes the process of retrieving, storing, and transferring semiconductor wafer containers into or out of the stocker slow and tedious. Since retrieval and transfer of semiconductor wafer containers for delivery to a processing station is an important step in the process, it would be advantageous if the retrieval and transfer can be accelerated and made more efficient.
One object of the present invention is to provide a semi-open architecture for a semiconductor wafer container storage cabinet or stocker.
Another object of the present invention is to provide a semiconductor wafer storage container in which each input port or window is buffered.
It is therefore another object of the present invention to provide a semi-open architecture or kiosk stocker with each interior space buffered with an adjacent exterior space or slot.
Yet another object of the present invention is to provide a semiconductor wafer container kiosk construction that includes automatic detection of the position of each semiconductor wafer container.
Yet another object of the present invention is to provide a semiconductor wafer container kiosk that automatically advances and fills an open slot when a pick-up and transfer device retrieves a semiconductor wafer container.
Another object of the present invention is to provide an improved stocker that permits rapid replacement of multiple containers removed and transferred out of the stocker.
Still another object of the invention is to provide a drive and detection system to detect when a semiconductor wafer has been removed and automatically start a drive system to move a back up container into the empty space where the semiconductor wafer has been removed.
The purpose of the present invention is to provide a semiconductor storage cabinet known as a stocker having a semi-open architecture kiosk construction in which each internal storage position in the stocker has an external space acting as a buffer to fill an empty space when a semiconductor wafer is removed from an internal space or slot. The system facilitates the storage and retrieval of semiconductor wafer containers to improve the production of integrated circuit chips from semiconductor wafers.
The stocker of the present invention provides a semiconductor wafer container kiosk that is constructed of multiple identical sections forming approximately a semi-circular cabinet around a pick-up and transfer device. Five to seven sections, each identical form a structure around the pick-up or transfer device. The number of sections depends upon the size of the semiconductor wafer containers being stored for processing. Larger, 300 mm (12xe2x80x3 wafers) containers limit the number of sections to five while the smaller, 180 mm (8xe2x80x3 wafers) containers allow up to identical seven sections forming the semi-circular kiosk.
Each section of the five section storage kiosk has a vertical panel with two input ports or windows one above the other allowing storage of up to ten semiconductor wafer containers in the kiosk. The shelves for supporting the semiconductor wafer containers extend outside the kiosk so that each storage slot inside the kiosk is xe2x80x9cbufferedxe2x80x9d by a second semiconductor wafer container accessible from outside the kiosk resulting in a doubling the capacity to ten buffered storage spaces or slots for a total storage space of up to twenty containers of the larger wafers or up to twenty-eight containers of the smaller wafers.
Each shelf both inside and outside the kiosk has a drive and detection system for advancing and replacing a semiconductor wafer container automatically upon a removal of a cassette or container by the pick-up and transfer system. The shelves have a pair of side rails joined by cross bars to provide support. Mounted on and between the side rails are a plurality of rollers for supporting a semiconductor wafer container that is positioned in the storage space. A separate shelf having a detector and drive system is provided at each storage space or slot both inside and outside the stocker. A shelf on an exterior position is adjacent to and in alignment with an identically constructed shelf on the interior of the kiosk. The rollers on one side of the shelf are attached to the adjacent side rail and connect to a drive motor inside the side rail. Idler rollers are mounted on the opposite side rail.
A photo-detector responds to indicate a semiconductor wafer container has been picked up and removed. This activates a drive system to move a back-up cassette into the space or slot where the cassette was removed. A photo-detector is provided at a front end of one of the side rails for detecting when a shelf or position is empty or filled with a semiconductor wafer container. Each detector is connected with the system electronics and provides a signal when there is a change at any one of the interior or exterior positions of the stocker. The detectors indicate when there is a change at any one of the positions in the stocker. Thus whenever a semiconductor wafer cassette is picked up and removed by pick-up and transfer device, the detectors in the interior shelf and adjacent exterior shelf tell the system to move the cassette in the buffer position forward filling the empty interior space or slot. The system permits a semiconductor wafer cassette stocker to be re-filled in minutes rather than the much longer times with present stockers.
An advantage of this device and construction is the kiosk stocker can be re-filled quickly as each internal shelf or slot is backed-up or buffered with an external shelf allowing rapid refilling of empty slots. In present stockers replacement of removed containers is agonizingly slow as there is usually only one port to input new containers. As each container is placed on a shelf, adjacent input port the pick-up and transfer system must pick the container up, move to an open space or shelf inside the stocker then return to the input port from another container. In contrast the kiosk stocker allows replacement of ten to fourteen containers in minutes or in almost the same time it takes to replace a single container in the present stockers.
The semiconductor wafer cassette storage system is comprised of a plurality of identical sections forming a semi-open architecture around a pick-up and transfer system for retrieving semiconductor storage containers on shelves in the interior of the stocker. Each identical section of the stocker has a vertical panel with a port or window for mounting two interior shelves and two exterior shelves one above the other. Each exterior shelf backs up an interior shelf. The back up shelves act as a buffer or temporary storage ready to immediately and automatically fill a space and replace a semiconductor wafer container removed from the stocker by pick-up and transfer device.
The above and other objects, advantages, and novel features of the invention will be more fully understood from the following detailed description and the accompanying drawings, in which: